Controller and control method for internal combustion engine

Abstract

A controller for an internal combustion engine is configured to control a vehicle internal combustion engine having a crankshaft connected to a manual transmission via a clutch. The controller is configured to execute a feedback process, a torque control process, an assist process, a fixing process, and a gradual decrease process. The fixing process includes fixing a correction coefficient at a specified value on condition that the clutch is in a transition period from the disengaged state to the engaged state. The gradual decrease process includes stopping the fixing process and gradually decreasing the correction coefficient to the feedback operation amount when the fixing process is executed and the assist torque is smaller than or equal to a predetermined value.

1 . A controller for an internal combustion engine being configured to control a vehicle internal combustion engine having a crankshaft connected to a manual transmission via a clutch, the controller being configured to execute:
 a feedback process of calculating a feedback operation amount, which is an operation amount used to perform feedback control to set a rotational speed of the crankshaft of the internal combustion engine to a target rotational speed;   a torque control process of controlling a torque of the internal combustion engine by using, as an input, an idle required torque, which is a value obtained by multiplying a base torque by a correction coefficient;   an assist process of raising the base torque by an assist torque, which is a torque used to limit a decrease in the rotational speed of the crankshaft that accompanies transition of the clutch from a disengaged state to an engaged state;   a fixing process of fixing the correction coefficient at a specified value on condition that the clutch is in a transition period from the disengaged state to the engaged state; and   a gradual decrease process of stopping the fixing process and gradually decreasing the correction coefficient to the feedback operation amount when the fixing process is executed and the assist torque is smaller than or equal to a predetermined value.   
     
     
         2 . The controller for an internal combustion engine according to  claim 1 , wherein
 the fixing process is a process of fixing the correction coefficient at the specified value when following two conditions are met: a condition that the clutch is in the transition period; and a condition that an accelerator is being operated, and   the controller is configured to use the feedback operation amount as the correction coefficient when the fixing process is not executed.   
     
     
         3 . The controller for an internal combustion engine according to  claim 1 , the controller being configured to
 execute the fixing process on condition that the feedback operation amount is smaller than a specified value, and   in a case in which the feedback operation amount is greater than the specified value, use the feedback operation amount as the correction coefficient even if the clutch is in the transition period.   
     
     
         4 . The controller for an internal combustion engine according to  claim 1 , wherein the controller is configured to, in a case in which the feedback operation amount is smaller than the specified value, execute a gradual increase process of gradually increasing the correction coefficient from the value of the feedback operation amount to the specified value prior to starting of the fixing process. 
     
     
         5 . The controller for an internal combustion engine according to  claim 1 , wherein the assist process includes a process of
 during the transition period, calculating the assist torque to be a greater value when a decrease rate of the rotational speed of the crankshaft is high than when the decrease rate is low, and   gradually decreasing the assist torque to zero when the transition period is complete and the clutch is in the engaged state.   
     
     
         6 . The controller for an internal combustion engine according to  claim 1 , wherein
 the controller is configured to execute an accelerator required torque calculation process of calculating an accelerator required torque of the internal combustion engine in accordance with an accelerator operation amount, and   the torque control process includes a process of
 using the accelerator required torque as an input in addition to the idle required torque, and 
 controlling the torque of the internal combustion engine in accordance with a greater one of the idle required torque and the accelerator required torque. 
   
     
     
         7 . The controller for an internal combustion engine according to  claim 1 , wherein the gradual decrease process includes a process of setting a gradual decrease rate of the correction coefficient to a smaller value when a vehicle speed is low than when the vehicle speed is high. 
     
     
         8 . A method of controlling a vehicle internal combustion engine having a crankshaft connected to a manual transmission via a clutch, the method comprising:
 executing a feedback process of calculating a feedback operation amount, which is an operation amount used to perform feedback control to set a rotational speed of the crankshaft of the internal combustion engine to a target rotational speed;   executing a torque control process of controlling a torque of the internal combustion engine by using, as an input, an idle required torque, which is a value obtained by multiplying a base torque by a correction coefficient;   executing an assist process of raising the base torque by an assist torque, which is a torque used to limit a decrease in the rotational speed of the crankshaft that accompanies transition of the clutch from a disengaged state to an engaged state;   executing a fixing process of fixing the correction coefficient at a specified value on condition that the clutch is in a transition period from the disengaged state to the engaged state; and   executing a gradual decrease process of stopping the fixing process and gradually decreasing the correction coefficient to the feedback operation amount when the fixing process is executed and the assist torque is smaller than or equal to a predetermined value.   
     
     
         9 . A controller for an internal combustion engine being configured to control a vehicle internal combustion engine having a crankshaft connected to a manual transmission via a clutch, wherein
 the controller comprises processing circuitry, and   the processing circuitry is configured to execute
 a feedback process of calculating a feedback operation amount, which is an operation amount used to perform feedback control to set a rotational speed of the crankshaft of the internal combustion engine to a target rotational speed; 
 a torque control process of controlling a torque of the internal combustion engine by using, as an input, an idle required torque, which is a value obtained by multiplying a base torque by a correction coefficient; 
 an assist process of raising the base torque by an assist torque, which is a torque used to limit a decrease in the rotational speed of the crankshaft that accompanies transition of the clutch from a disengaged state to an engaged state; 
 a fixing process of fixing the correction coefficient at a specified value on condition that the clutch is in a transition period from the disengaged state to the engaged state; and 
 a gradual decrease process of stopping the fixing process and gradually decreasing the correction coefficient to the feedback operation amount when the fixing process is executed and the assist torque is smaller than or equal to a predetermined value.